UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 02549

                                ----------------

                                   FORM 10-K/A

                          Amendment No. 3 to Form 10-K

                        FOR ANNUAL AND TRANSITION REPORTS
                     PURSUANT TO SECTIONS 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

       [x] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
                              EXCHANGE ACT OF 1934

                  For the fiscal year ended: December 31, 2002

                                       OR

     [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
                              EXCHANGE ACT OF 1934

                  For the transition period from _____ to _____

                         Commission File Number: 1-7211

                              IONICS, INCORPORATED
             (Exact name of registrant as specified in its charter)

      Massachusetts                                      04-2068530
(State of incorporation)                    (IRS Employer Identification Number)

      65 Grove Street                                    02472-2882
 Watertown, Massachusetts                                (Zip Code)
(Address of principal executive offices)

       Registrant's telephone number, including area code: (617) 926-2500

 Securities registered pursuant to Section 12(b) of the Act:
                         Common Stock, $1.00 par value

       Name of each exchange on which registered: New York Stock Exchange

        Securities registered pursuant to Section 12(g) of the Act: None

         Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports) and (2) has been subject to such
filing requirements for the past 90 days.

                                  Yes X      No ___

     Indicate by check mark if disclosure of delinquent  filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's  knowledge,  in definitive proxy or information  statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K.        [X]

         Indicate by check mark whether the registrant is an accelerated filer
(as defined in Rule 12b-2 of the Act).

                                  Yes _X      No ___

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<PAGE>

         The aggregate market value of the Common Stock of the registrant held
by non-affiliates as of June 28, 2002 was $415,244,560 (17,123,487 shares at
$24.25 per share) (includes shares owned by a trust for the indirect benefit of
a non-employee director, and by a trust for the indirect benefit of a spouse of
a non-employee director).

         As of March 21, 2003, 17,555,046 shares of Common Stock, $1.00 par
value, were issued and outstanding.


                       DOCUMENTS INCORPORATED BY REFERENCE

On April 9, 2003 the Registrant filed a definitive proxy statement pursuant to
Regulation 14A. Portions of such proxy statement are incorporated by reference
into Part III of this Annual Report on Form 10-K.



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                                EXPLANATORY NOTE

Ionics, Incorporated (the "Company") is filing this Amendment No. 3 to Form 10-K
to amend its Annual  Report on Form 10-K for the year ended  December  31, 2002,
originally  filed on March 31,  2003 and  amended  on April 1, 2003 and June 26,
2003, to clarify the disclosure  previously made with respect to Item 14 of Part
III, "Controls and Procedures."

The Company hereby amends in its entirety Item 14 of Part III to read as
follows:

ITEM 14. CONTROLS AND PROCEDURES

As part of the Company's continuing efforts to ensure that information required
to be disclosed by the Company in its Securities and Exchange Commission filings
is appropriately accumulated and disseminated to allow timely decisions
regarding required disclosure, the Company has been taking various actions to
strengthen its system of internal controls and disclosure controls and
procedures. Such actions were also taken to enhance the processes by which the
Company manages its various divisions and subsidiaries, because managing a large
number of relatively small, locally managed businesses around the world presents
significant challenges.

Prior to the evaluation of the Company's disclosure controls and procedures made
in connection with the filing of its Quarterly Report on Form 10-Q for the
periods ended September 30, 2002, the Company made changes in its internal
controls and took other actions designed to enhance the Company's internal
controls, which consisted of the following:

o    the hiring of new personnel including, two new segment controllers in April
     and July of 2002, three new divisional  controllers in May and September of
     2002,  a  corporate  director  of  accounting  in  July  2002,  and  a  new
     consolidation  accountant in September  2002, to enhance the quality of its
     accounting  capabilities;
o    the replacement of the senior  operating  executive at the Company's French
     subsidiary and the  reassignment of much of the operational  responsibility
     for that subsidiary to the Company's Italian subsidiary;
o    the implementation of a new financial consolidation software package (which
     became operational in September 2002);
o    the  implementation  of a centralized  bid and proposal review and approval
     process at the beginning of 2002;
o    the  expansion of the internal  audit  function  through the use of outside
     resources beginning in March 2002;
o    the formalization of certain accounting and information technology policies
     and  procedures  at various  times  throughout  the year;
o    the hiring of a Director of Project  Management  in October 2002 to oversee
     project-related  procedures  and to train project  managers at locations to
     enable them to better comply with Company goals,  policies and  procedures;
     and
o    the institution of procedures  requiring written  quarterly  certifications
     and  representations  from the head of each  business  group  and the local
     controller of each business location.

Since that evaluation in November 2002, the Company has made additional changes
in its internal controls and taken other actions designed to enhance the
Company's internal controls, which consisted of the following:

o    the formation of a disclosure committee to oversee the effectiveness of the
     Company's disclosure controls and procedures;
o    in  furtherance  of the  centralized  bid and proposal  review and approval
     process, the establishment of formal,  systematic  procedures for reviewing
     all major commercial  projects being  undertaken by the Company,  including
     monthly participation by senior management;
o    the  finalization  of a project  database to  facilitate  the  tracking and
     analysis of project performance throughout the Company in December 2002;
o    the hiring of a senior financial manager into a newly created position as
     European Controller in December 2002, who is responsible for providing
     financial oversight and control for the Equipment Business Group's European
     operations; and
o    the conduct of a conference, and other educational activities, for the
     Company's segment and divisional controllers and corporate accounting
     staff, which included programs regarding, among other topics, inter-company
     transactions, key policies under U.S. generally accepted accounting
     principles (e.g., SAB 101, SOP 81-1), the Sarbanes-Oxley Act of 2002,
     internal controls, U.S. regulation of international transactions, and key
     responsibilities of the local controllers.

In connection with the audit of its financial statements for 2002, the Company
was advised by its independent auditors that certain of its internal controls
had deficiencies and material control weaknesses. Throughout the first quarter
of 2003 (including both during the period in which the audit was being conducted
and after it had been completed but prior to the evaluation referred to below),
the Company had been addressing the issues cited by its independent auditors. As
discussed above, during this period, the Company's disclosure committee was
functioning, the procedures requiring written quarterly certifications and
representations from the head of each business group and the local controller of
each business location had been instituted, and the Company had implemented the
review procedures for major commercial projects, conducted numerous educational
activities for its segment and divisional controllers and corporate accounting
staff, and continued updating its accounting policies and procedures. During the
first quarter of 2003 (but prior to the evaluation referred to below), the
Company's senior management conducted detailed and intensive reviews of the
Company's financial statements and related disclosures and matters identified by
the independent auditors and internal auditors during their respective audit
processes.

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<PAGE>


With the goal of further improving the quality and timeliness of the information
available to management, the Company is continuing to implement measures
designed to address the deficiencies and weaknesses cited by its independent
auditors as follows:

o    to evaluate and  strengthen  its financial and  accounting  staff and their
     knowledge and understanding of key policies under U.S.  generally  accepted
     accounting principles and of their responsibilities;
o    to improve  monitoring  controls to assure the  prevention  or detection of
     material accounting errors on a timely basis;
o    to reduce the time necessary to collect and report  financial and operating
     data by improving the timing and accuracy of  forecasting  and  emphasizing
     more frequent reviews of the Company's balance sheets and reconciliation of
     intercompany balances;
o    to continue to update its accounting policies and procedures.

In March 2003, the Company carried out an evaluation, under the supervision and
with the participation of the Company's management, including the Company's
Chief Executive Officer and Chief Financial Officer, of the effectiveness of the
Company's "disclosure controls and procedures." The SEC defines "disclosure
controls and procedures" as a company's controls and other procedures that are
designed to ensure that information required to be disclosed by the company in
the reports it files or submits under the Securities Exchange Act of 1934 is
recorded, processed, summarized and reported, within the time periods specified
in the SEC's rules and forms. Based on their evaluation of the Company's
disclosure controls and procedures, the Company's then Chief Executive Officer
(principal executive officer) and Chief Financial Officer (principal financial
officer) concluded that the Company's disclosure controls and procedures were
substantially effective for these purposes as of the date of the evaluation.
This conclusion reflected the certifying officers' determination, based on their
evaluation as of the evaluation date, that these procedures were effective in
recording, processing, summarizing and reporting the substantive information
necessary for the Company to meet its reporting obligations on a timely basis
but that the process could function more efficiently. The certifying officers
believed that the efficiency of the process would benefit from the actions
described above that were implemented prior to their evaluation. In addition,
the certifying officers believe that implementation of additional measures
designed to address the deficiencies and material control weaknesses cited by
the Company's independent auditors as described in the preceding paragraph will
further improve the efficiency of this process.

There were no significant changes in the Company's internal controls or in other
factors that could significantly affect the Company's internal controls between
March 27, 2003 (the date of the above-referenced evaluation of such controls)
and March 31, 2003 (the date of the filing of the Company's Annual Report on
Form 10-K for the fiscal year ended December 31, 2002).


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Item 15. Exhibits, Financial Statement Schedules and Reports on Form 10-K

Exhibit No.    Description
-----------    -----------

  31.0         Rule 13a-14(a)/15d-14(a) Certifications

               31.1     Rule 13a-14(a) Certification of Chief Executive Officer.

               31.2     Rule 13a-14(a) Certification of Chief Financial Officer.

  32.0         Section 1350 Certifications

               32.1     Section 1350 Certification of Chief Executive Officer.

               32.2     Section 1350 Certification of Chief Financial Officer.





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                                   SIGNATURES


Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this amendment to be signed on its behalf by the
undersigned, thereunto duly authorized.

                                  IONICS, INCORPORATED
                                  (Registrant)

Date:  October 2, 2003            By: /s/ Stephen Korn
                                      ----------------
                                  Stephen Korn
                                  Vice President and
                                  General Counsel





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                                  EXHIBIT INDEX

Exhibit No.  Description
-----------  -----------

31.0         Rule 13a-14(a)/15d-14(a) Certifications

             31.1       Rule 13a-14(a) Certification of Chief Executive Officer.

             31.2       Rule 13a-14(a) Certification of Chief Financial Officer.

32.0         Section 1350 Certifications

             32.1       Section 1350 Certification of Chief Executive Officer.

             32.2       Section 1350 Certification of Chief Financial Officer.





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                                  EXHIBIT 31.1

                                 CERTIFICATIONS


I, Douglas R. Brown, certify that:

1.   I have reviewed this Annual Report on Form 10-K, as amended, of Ionics,
     Incorporated;

2.   Based on my knowledge, this report does not contain any untrue statement of
     a material fact or omit to state a material fact necessary to make the
     statements made, in light of the circumstances under which such statements
     were made, not misleading with respect to the period covered by this
     report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this report, fairly present in all material
     respects the financial condition, results of operations and cash flows of
     the registrant as of, and for, the periods presented in this report;

4.   The registrant's other certifying officer(s) and I are responsible for
     establishing and maintaining disclosure controls and procedures (as defined
     in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

         (a) Designed such disclosure controls and procedures, or caused such
         disclosure controls and procedures to be designed under our
         supervision, to ensure that material information relating to the
         registrant, including its consolidated subsidiaries, is made known to
         us by others within those entities, particularly during the period in
         which this report is being prepared;

         (b) [Paragraph omitted in accordance with SEC transition instructions
         contained in SEC Release 34-47986];

         (c) Evaluated the effectiveness of the registrant's disclosure controls
         and procedures and presented in this report our conclusions about the
         effectiveness of the disclosure controls and procedures, as of the end
         of the period covered by this report based on such evaluation; and

         (d) Disclosed in this report any change in the registrant's internal
         control over financial reporting that occurred during the registrant's
         most recent fiscal quarter (the registrant's fourth fiscal quarter in
         the case of an annual report) that has materially affected, or is
         reasonably likely to materially affect, the registrant's internal
         control over financial reporting; and

5.   The registrant's other certifying officer(s) and I have disclosed, based on
     our most recent evaluation of internal control over financial reporting, to
     the registrant's auditors and the audit committee of registrant's board of
     directors (or persons performing the equivalent functions):

         (a) All significant deficiencies and material weaknesses in the design
         or operation of internal control over financial reporting which are
         reasonably likely to adversely affect the registrant's ability to
         record, process, summarize and report financial information;

         (b) Any fraud, whether or not material, that involves management or
         other employees who have a significant role in the registrant's
         internal control over financial reporting.


Date: October 2, 2003                               /s/ Douglas R. Brown
                                                    --------------------
                                                    Douglas R. Brown
                                                    Chief Executive Officer




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                                  EXHIBIT 31.2

                                 CERTIFICATIONS


I, Daniel M. Kuzmak, certify that:

1. I have reviewed this Annual Report on Form 10-K, as amended, of Ionics,
Incorporated;

2. Based on my knowledge, this report does not contain any untrue statement of a
material fact or omit to state a material fact necessary to make the statements
made, in light of the circumstances under which such statements were made, not
misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial
information included in this report, fairly present in all material respects the
financial condition, results of operations and cash flows of the registrant as
of, and for, the periods presented in this report;

4. The registrant's other certifying officer(s) and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:

         (a) Designed such disclosure controls and procedures, or caused such
         disclosure controls and procedures to be designed under our
         supervision, to ensure that material information relating to the
         registrant, including its consolidated subsidiaries, is made known to
         us by others within those entities, particularly during the period in
         which this report is being prepared;

         (b) [Paragraph omitted in accordance with SEC transition instructions
         contained in SEC Release 34-47986];

         (c) Evaluated the effectiveness of the registrant's disclosure controls
         and procedures and presented in this report our conclusions about the
         effectiveness of the disclosure controls and procedures, as of the end
         of the period covered by this report based on such evaluation; and

         (d) Disclosed in this report any change in the registrant's internal
         control over financial reporting that occurred during the registrant's
         most recent fiscal quarter (the registrant's fourth fiscal quarter in
         the case of an annual report) that has materially affected, or is
         reasonably likely to materially affect, the registrant's internal
         control over financial reporting; and

5. The registrant's other certifying officer(s) and I have disclosed, based on
our most recent evaluation of internal control over financial reporting, to the
registrant's auditors and the audit committee of registrant's board of directors
(or persons performing the equivalent functions):

         (a) All significant deficiencies and material weaknesses in the design
         or operation of internal control over financial reporting which are
         reasonably likely to adversely affect the registrant's ability to
         record, process, summarize and report financial information;

         (b) Any fraud, whether or not material, that involves management or
         other employees who have a significant role in the registrant's
         internal control over financial reporting.


Date: October 2, 2003                              /s/ Daniel M. Kuzmak
                                                   --------------------
                                                   Daniel M. Kuzmak
                                                   Vice President, Finance and
                                                   Chief Financial Officer




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                                  EXHIBIT 32.1

    CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO
                 SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

         In connection with the Annual Report of Ionics, Incorporated (the
"Company") on Form 10-K, as amended, for the period ending December 31, 2002 as
filed with the Securities and Exchange Commission on the date hereof (the
"Report"), I, Douglas R. Brown, Chief Executive Officer of the Company, certify,
pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, that:

         (1) The Report fully complies with the requirements of section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

         (2) The information contained in the Report fairly presents, in all
material respects, the financial condition and results of operations of the
Company.


                                                     /s/ Douglas R. Brown
                                                     --------------------
                                                     Douglas R. Brown
                                                     Chief Executive Officer
                                                     October 2, 2003




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                                  EXHIBIT 32.2

    CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO
                 SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

         In connection with the Annual Report of Ionics, Incorporated (the
"Company") on Form 10-K, as amended, for the period ending December 31, 2002 as
filed with the Securities and Exchange Commission on the date hereof (the
"Report"), I, Daniel M. Kuzmak, Vice President, Finance and Chief Financial
Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

         (1) The Report fully complies with the requirements of section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

         (2) The information contained in the Report fairly presents, in all
material respects, the financial condition and results of operations of the
Company.


                                                    /s/ Daniel M. Kuzmak
                                                    --------------------
                                                    Daniel M. Kuzmak
                                                    Vice President, Finance and
                                                    Chief Financial Officer
                                                    October 2, 2003